I attached a brand new Seagate USB SSD drive (Backup Plus Slim) to a MacBook Pro running 10.15.2. It mounted the first time, I could see it in Finder, and was able to run the Mac start up program on the drive. However this did not seem to work, so I disconnected the drive. I thought I ejected it properly but not absolutely sure.
Then when I plugged it in again, I could not see it in Finder. I also tried on a Mac mini running 10.14.6 but could not see it in Finder either. Back on the MacBook Pro, I tried Disk Utility. It found the disk, but it was greyed out and not mounted. When I tried to mount it, I saw the following error:
Could not mount “disk2s2”. (com.apple.DiskManagement.disenter error -119930868.)
Doing a search on Google, I found this discussion, which indicates it is a Catalina problem. I could not see any useful answer.
I have tried waiting for hours for it to fix itself and rebooting my machine, but it appears that the disk has become damaged. How do I fix this?